What is the timing of expense reimbursement to employees?

I don't think they are unreasonable, however some items to consider:

Do employees use their own credit cards?
What is your threshold for receipts?
What if an employee is out (on the road, ill)?
Do you take weekly reports or only monthly?

Additionally,

Do you have an automated system for expense submission?
Do you pay by check or ACH?
Is the expense policy simple or complex?
Is it built into the automated system, if one is used?

I think waiting on submission/approval will always result in timing issues. People are just not good at timely T&E.

What system do you use? We used to use Concur, which has reports that allow you to make accruals based on expense reports in process (various stages) and credit card transactions not yet added onto expense reports.

There are always out-of-pocket costs, but I've never experienced that we needed to get more detailed /exhaustive in chasing those down. If we were aware of something going on (like a specific meeting or event) we'd just top off as needed.

No way to absolutely perfect an accrual but at least our approach had "legs" under it.

If you really want to shorten month end close, go to weekly expense reimbursements. That is more fair to the employee and it lessens month end crunch. Use strict cut-offs (reports in by Monday at 9 get paid by Wednesday at noon as an example). If you don't have reimbursement requests in by month end close, accrue rather than chase the actual. The above will shorten your cycle considerably.

Twice a month with payroll works best for me. But later when exceptions require manager approvals outside of policy is always OK. Must be received 2 days before reimbursement, all reimbursements by direct deposit.
Sometimes the staff will rush a payment or expedite when pushed or unusual circumstances warrant it, but that is their call and between them and the individual involved. But I rarely push them or bend the policy, and let them everyone know the rules and expect the same treatment.

I agree with Lyle. Get them in a routine to submit expense reports at the end of each week. You can pay them in a subsequent payroll, but at least you have the expenses captured. Many companies use software to submit and approve reports and accounting gets the data immediately upon approval to record and pay. In some instances accounting reviews detail receipts etc. after the fact which have been scanned.

Not sure of the size of your company, but consider asking them to submit expenses frequently/weekly upon incurred, then you reimburse them on set days in month, e.g., 2nd and 4th Wednesday, depending on $ amount. You need time for approval and processing. Agree with others that need to rules are for everyone, not someone else.

It is definitely reasonable for Finance to set these rules as the owner of the process, especially if you provide tools for employees to be able to easily create, submit, and review expense reports. We have found that the right process tools result in employees themselves speeding up their timeline to almost exactly what you are hoping to achieve for 2 reasons: they want to be reimbursed earlier and holding on to expenses makes it much more painful for them. I have a short case study that outlines this (happy to share).

You could create an incentive that leads employees to follow the rules and the one I can think of is that you set specific reimbursement deadlines. For example, you could state you will only do 2 reimbursement runs per month and to be included in a run, there is a deadline for the expense report to be submitted 2 days prior. Having to wait 2 more weeks for reimbursement will cause at least some employees to follow the rule.

Wayne's list of questions is a good starting point. Company credit cards can be an issue if they are direct-billed to the company so employees have low incentive to do their expenses but there are ways to make that happen as well.

Good luck.